1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2020, Google Inc.
*
* extensible.cpp - Utilities to create extensible public classes with stable ABIs
*/
#include <libcamera/extensible.h>
/**
* \file extensible.h
* \brief Utilities to create extensible public classes with stable ABIs
*/
namespace libcamera {
/**
* \def LIBCAMERA_DECLARE_PRIVATE
* \brief Declare private data for a public class
* \param klass The public class name
*
* The LIBCAMERA_DECLARE_PRIVATE() macro plumbs the infrastructure necessary to
* make a class manage its private data through a d-pointer. It shall be used at
* the very top of the class definition, with the public class name passed as
* the \a klass parameter.
*/
/**
* \def LIBCAMERA_DECLARE_PUBLIC
* \brief Declare public data for a private class
* \param klass The public class name
*
* The LIBCAMERA_DECLARE_PUBLIC() macro is the counterpart of
* LIBCAMERA_DECLARE_PRIVATE() to be used in the private data class. It shall be
* used at the very top of the private class definition, with the public class
* name passed as the \a klass parameter.
*/
/**
* \def LIBCAMERA_D_PTR(klass)
* \brief Retrieve the private data pointer
* \param[in] klass The public class name
*
* This macro can be used in any member function of a class that inherits,
* directly or indirectly, from the Extensible class, to create a local
* variable named 'd' that points to the class' private data instance.
*/
/**
* \def LIBCAMERA_O_PTR(klass)
* \brief Retrieve the public instance corresponding to the private data
* \param[in] klass The public class name
*
* This macro is the counterpart of LIBCAMERA_D_PTR() for private data classes.
* It can be used in any member function of the private data class to create a
* local variable named 'o' that points to the public class instance
* corresponding to the private data.
*/
/**
* \class Extensible
* \brief Base class to manage private data through a d-pointer
*
* The Extensible class provides a base class to implement the
* <a href="https://wiki.qt.io/D-Pointer">d-pointer</a> design pattern (also
* known as <a href="https://en.wikipedia.org/wiki/Opaque_pointer">opaque pointer</a>
* or <a href="https://en.cppreference.com/w/cpp/language/pimpl">pImpl idiom</a>).
* It helps creating public classes that can be extended without breaking their
* ABI. Such classes store their private data in a separate private data object,
* referenced by a pointer in the public class (hence the name d-pointer).
*
* Classes that follow this design pattern are referred herein as extensible
* classes. To be extensible, a class PublicClass shall:
*
* - inherit from the Extensible class or from another extensible class
* - invoke the LIBCAMERA_DECLARE_PRIVATE() macro at the very top of the class
* definition
* - define a private data class named PublicClass::Private that inherits from
* the Private data class of the base class
* - invoke the LIBCAMERA_DECLARE_PUBLIC() macro at the very top of the Private
* data class definition
* - pass a pointer to a newly allocated Private data object to the constructor
* of the base class
*
* Additionally, if the PublicClass is not final, it shall expose one or more
* constructors that takes a pointer to a Private data instance, to be used by
* derived classes.
*
* The Private class is fully opaque to users of the libcamera public API.
* Internally, it can be kept private to the implementation of PublicClass, or
* be exposed to other classes. In the latter case, the members of the Private
* class need to be qualified with appropriate access specifiers. The
* PublicClass and Private classes always have full access to each other's
* protected and private members.
*/
/**
* \brief Construct an instance of an Extensible class
* \param[in] d Pointer to the private data instance
*/
Extensible::Extensible(Extensible::Private *d)
: d_(d)
{
}
/**
* \var Extensible::d_
* \brief Pointer to the private data instance
*/
/**
* \class Extensible::Private
* \brief Base class for private data managed through a d-pointer
*/
/**
* \brief Construct an instance of an Extensible class private data
* \param[in] o Pointer to the public class object
*/
Extensible::Private::Private(Extensible *o)
: o_(o)
{
}
Extensible::Private::~Private()
{
}
/**
* \var Extensible::Private::o_
* \brief Pointer to the public class object
*/
} /* namespace libcamera */
|
